Vulnerability Overview
- CVE ID: CVE-2025-58107
- Affected Product: Microsoft Exchange Server (On-Premises)
- Affected Component: Exchange ActiveSync (EAS)
- Affected Versions: Microsoft Exchange Server up to Exchange 2019
- Vulnerability Type: Sensitive Information Exposure
- CWE: CWE-200 – Exposure of Sensitive Information to an Unauthorized Actor
- CVSS v3.1 Score: 7.5
- Severity: High
- Attack Vector: Network
- Attack Complexity: Low
- Privileges Required: None
- User Interaction: None
- Scope: Unchanged
- Confidentiality Impact: High
- Integrity Impact: None
- Availability Impact: None
- Exploitability: High
- Exploit Availability: No confirmed weaponized exploit publicly released yet (research PoC reported)
- Discovery Context: Information disclosure during ActiveSync communication
This vulnerability affects Microsoft Exchange servers where Exchange ActiveSync is used for mobile synchronization. Under certain configurations, sensitive information transmitted by Samsung mobile devices may be sent in cleartext over the network. Data that may become exposed includes usernames, email addresses, device identifiers, authentication tokens, and Base64-encoded passwords.
Technical Description
CVE-2025-58107 is classified as a sensitive information exposure vulnerability in the Microsoft Exchange ActiveSync (EAS) service.
Exchange ActiveSync is widely used for synchronizing emails, contacts, and calendar data between Microsoft Exchange servers and mobile devices. During the synchronization process, authentication and device information are exchanged between the mobile device and the Exchange server.
In affected configurations, it has been observed that sensitive authentication and device information may be transmitted without sufficient protection. As a result, sensitive parameters such as:
- Username
- Email address
- Device ID
- Authentication bearer token
- Base64-encoded password
may appear in network traffic in readable form.
Base64 encoding is not encryption. It is simply an encoding method that can be easily reversed. If captured by an attacker, the encoded value can be decoded to reveal the original credentials.
Because this communication may occur during routine mobile synchronization, the exposure can happen without any suspicious activity from the user’s perspective.
Root Cause Analysis
The vulnerability is primarily caused by improper handling of authentication parameters within Exchange ActiveSync communications when interacting with certain mobile device implementations.
Key contributing factors include:
- Legacy authentication mechanisms used by some mobile clients
- Improper protection of authentication tokens during synchronization
- Transmission of authentication data without strong transport protection in some scenarios
- Weak encoding methods used for credential fields
When such conditions occur simultaneously, sensitive information may be exposed within HTTP requests generated by the ActiveSync protocol.
Affected Environment
The issue is mainly observed in environments where:
- Microsoft Exchange Server (on-premises) is deployed
- Exchange ActiveSync is enabled
- Samsung mobile devices connect through ActiveSync
- Legacy authentication or weak configuration exists
Cloud-hosted Exchange environments typically enforce stricter authentication controls and are less likely to be affected.
Attack Scenario
Exploitation of this vulnerability generally involves network interception rather than direct server exploitation.
A typical attack path may occur as follows:
- A mobile device connects to an Exchange server using ActiveSync.
- The device sends synchronization requests to the
/Microsoft-Server-ActiveSyncendpoint. - Authentication headers and device metadata are transmitted during the request.
- Sensitive parameters are transmitted using weak encoding or without proper protection.
- A network attacker captures the traffic.
- The attacker extracts credentials or authentication tokens.
- The captured credentials are used to access the mailbox or Exchange services.
Since the attack requires only network access and no authentication, it is considered low complexity and remotely exploitable.
Proof of Concept (Educational Purposes Only)
A simple demonstration can be performed by monitoring ActiveSync traffic in a controlled testing environment.
Example captured request:
POST /Microsoft-Server-ActiveSync HTTP/1.1
Host: exchange.example.com
User-Agent: SamsungEAS/14.0
Authorization: Basic QWxhZGRpbjpPcGVuU2VzYW1l
X-MS-DeviceID: SAMSUNG-DEVICE-12345
X-MS-DeviceType: SamsungDevice
X-MS-PolicyKey: 123456789
Content-Type: application/vnd.ms-sync.wbxml
Captured parameters may include:
[email protected]
[email protected]
deviceId=SAMSUNG-DEVICE-12345
token=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9
password=YmFzZTY0UGFzc3dvcmQ=
Decoding example:
echo "YmFzZTY0UGFzc3dvcmQ=" | base64 -d
Output:
base64Password
This demonstrates how easily encoded credentials can be recovered if network traffic is intercepted.
Exploitation Possibilities
If sensitive credentials or tokens are captured, several follow-on attacks become possible.
Possible attacker actions may include:
- Unauthorized mailbox access
- Email data exfiltration
- Credential reuse in other corporate services
- Internal reconnaissance through email communication analysis
- Identity impersonation
Because email accounts often contain sensitive business information, this vulnerability can lead to serious data leakage incidents.
MITRE ATT&CK Mapping
| Tactic | Technique | Description |
|---|---|---|
| Credential Access | T1040 – Network Sniffing | Intercepting ActiveSync traffic |
| Credential Access | T1557 – Adversary-in-the-Middle | Intercepting authentication sessions |
| Credential Access | T1552 – Unsecured Credentials | Credentials exposed in network traffic |
| Collection | T1114 – Email Collection | Accessing mailbox contents |
| Initial Access | T1078 – Valid Accounts | Using stolen credentials |
Indicators of Compromise
Security teams may observe the following indicators:
- Suspicious ActiveSync authentication requests
- Unusual device identifiers
- Login attempts from new geographic locations
- Abnormal frequency of ActiveSync synchronization requests
- Reuse of authentication tokens across multiple IP addresses
- Base64 credential strings appearing in proxy or packet capture logs
Detection Methodology
Detection should focus on monitoring ActiveSync traffic, authentication behavior, and unusual device access patterns.
Important detection areas include:
- Exchange IIS logs
- Authentication logs
- Network packet capture data
- Proxy logs
- Mobile device synchronization logs
Monitoring for exposed credentials in HTTP headers or authentication tokens is critical.
Detection Rules
Splunk Query
index=exchange_logs
uri_path="/Microsoft-Server-ActiveSync"
| stats count by src_ip, user, user_agent, device_id
| sort -count
Microsoft Sentinel (KQL)
ExchangeHttpLogs
| where Url contains "Microsoft-Server-ActiveSync"
| summarize count() by ClientIP, UserAgent, DeviceId
| order by count_ desc
Elastic / Kibana Query
event.dataset:exchange* AND url.path:"/Microsoft-Server-ActiveSync"
Network Detection Query
http.request.uri contains "Microsoft-Server-ActiveSync"
AND http.request.headers.authorization contains "Basic"
Suricata IDS Rule
alert http any any -> any any (
msg:"Possible Exchange ActiveSync credential exposure";
content:"/Microsoft-Server-ActiveSync";
http_uri;
content:"Authorization: Basic";
http_header;
sid:5810701;
rev:1;
)
Log Sources for Detection
Security monitoring should include the following data sources:
- Exchange IIS logs
- Exchange ActiveSync logs
- Windows Event Logs
- Firewall logs
- Web proxy logs
- Network packet capture (PCAP)
- Mobile Device Management logs
- Identity provider authentication logs
These logs can reveal suspicious synchronization patterns and unauthorized mailbox access attempts.
Mitigation and Security Recommendations
Several defensive steps should be implemented to reduce the risk associated with this vulnerability.
Recommended actions:
- Ensure ActiveSync traffic is strictly enforced over HTTPS.
- Disable legacy authentication mechanisms.
- Restrict mobile device access to approved devices only.
- Implement conditional access policies.
- Monitor ActiveSync connections for abnormal behavior.
- Regularly review Exchange authentication logs.
- Deploy network monitoring tools to detect credential exposure.
Official Patch / Security Update
Microsoft Exchange security updates should be installed to mitigate this issue.
Official update documentation:
Administrators are advised to install the latest Exchange cumulative update and security update packages and review ActiveSync configuration settings after patching.
Security Impact Summary
CVE-2025-58107 demonstrates how legacy authentication mechanisms and weak transport handling can expose sensitive credentials in enterprise email infrastructure.
Although the vulnerability does not allow direct remote code execution, the exposure of authentication data can lead to credential compromise and unauthorized access to corporate email systems. Given the central role of email in organizational communication, the risk associated with this vulnerability should be treated with high priority in environments where Exchange ActiveSync is deployed.
